TWI392106B - Iii-nitride light emitting device with reduced polarization fields - Google Patents

Iii-nitride light emitting device with reduced polarization fields Download PDF

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Publication number
TWI392106B
TWI392106B TW94102469A TW94102469A TWI392106B TW I392106 B TWI392106 B TW I392106B TW 94102469 A TW94102469 A TW 94102469A TW 94102469 A TW94102469 A TW 94102469A TW I392106 B TWI392106 B TW I392106B
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device
layer
net polarization
spacer
difference
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TW94102469A
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TW200537712A (en
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Satoshi Watanabe
Stephen A Stockman
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Philips Lumileds Lighting Co
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    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES; ELECTRIC SOLID STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H01L33/00Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/02Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
    • H01L33/26Materials of the light emitting region
    • H01L33/30Materials of the light emitting region containing only elements of group III and group V of the periodic system
    • H01L33/32Materials of the light emitting region containing only elements of group III and group V of the periodic system containing nitrogen

Description

Group III nitride light-emitting device with reduced polarization field

This invention relates to a Group III nitride light-emitting device.

Semiconductor light-emitting devices including light-emitting diodes (LEDs), resonant cavity light-emitting diodes (RCLEDs), vertical-cavity laser diodes (VCSELs), and edge-emitting lasers are among the most effective currently available. Light source. The material systems of interest in the manufacture of high-intensity illumination devices capable of operating across the visible spectrum include III-V semiconductors, especially binary, ternary and quaternary alloys of gallium, aluminum, indium and nitrogen, also known as Group III nitride material. Typically, different groups are epitaxially grown by CMP, MOCVD, MBE, or other epitaxial techniques on sapphire, tantalum carbide, Group III nitride, or other suitable substrate. A stack of semiconductor layers of a portion and a dopant concentration is used to fabricate a Group III nitride light-emitting device. The stack generally includes: one or more n-type layers doped with, for example, Si, formed on the substrate; a luminescent or active region formed on the or the n-type layer; and formed on the active region It is doped with, for example, one or more p-type layers of Mg. The Group III nitride device formed on the conductive substrate may have p-contacts and n-contacts formed on opposite sides of the device. Typically, a Group III nitride device is fabricated on an insulating substrate such as sapphire with two contacts on the same side of the device. The devices are mounted such that light is extracted via a junction (referred to as an epitaxy-up device) or light is extracted (referred to as a flip chip device) relative to the surface of the contacts via the device.

Typically, the crystal layer in the Group III nitride device is grown as a strained wurtzite crystal on a lattice mismatched substrate such as sapphire. The crystals exhibit two types of polarization: spontaneous polarization due to differences in alloy composition between layers of different components, and piezoelectric polarization due to stress in the device layer. The total polarization in the layer is the sum of spontaneous and piezoelectric polarization.

1A is a cross-sectional view schematically illustrating a typical conventional strained wurtzite nitride double heterostructure semiconductor described in U.S. Patent No. 6,515,313. According to US Pat. No. 6,515,313, the substrate layer 1 can be any material suitable for growing a nitride semiconductor, including spinel (MgAl 2 O 4 ), sapphire (Al 2 O 3 ), SiC (including 6H, 4H and 3C). ), ZnS, ZnO, GaAs, AlN, and GaN. The thickness of the substrate is usually in the range of 100 μm to 1 mm. The buffer layer 2 on the substrate 1 may be formed of AlN, GaN, AlGaN, InGaN, or the like. This buffer layer promotes a possible lattice mismatch between the substrate layer 1 and the overlying conductive contact layer 3. However, if the substrate has a lattice constant approximately equal to the lattice constant of the nitride semiconductor, the buffer layer 2 can be omitted. The buffer layer 2 can also be omitted using certain nitride growth techniques. Depending on the composition of the material, the buffer layer may have an energy band gap in the range of 2.1 eV to 6.2 eV and may have a thickness of about 0.5 μm to 10 μm.

In general, the n-type contact layer 3 is also formed from a nitride semiconductor, preferably GaN or InGaN, having a thickness in the range of 0.5 μm to 5.0 μm, and the energy band gap is about 3.4 eV for GaN and for InGaN. Less (depending on the concentration of indium). The n-type or undoped plating layer 4 on the lower portion of the conductive layer 3 generally includes GaN or AlGaN, wherein the energy band gap is about 3.4 eV for GaN and more for AlGaN (depending on the Al concentration). Its thickness can range from 1 nm to 100 nm.

The nitride double heterostructure typically uses InGaN as the active region 5 on the lower plating layer, with a thickness ranging from 1 nm to 100 nm. The energy band gap of this layer is typically 2.8 eV for blue light emission, but it can vary depending on the indium concentration. The top p-type or undoped plating layer 6 on the active region is typically composed of AlGaN or GaN, and its thickness and band gap energy are similar to those of the lower n-type plating layer 4 and band gap energy. The p-type GaN conductive contact layer 7 on the plating layer 6 has an energy band gap of about 3.4 eV and a thickness of about 10 nm to 500 nm. Polarization-induced sheet charge occurs at the interface between the layers due to different constituent materials. Particularly interesting for the operation of the illuminator is the polarization induced sheet charge adjacent to the active region 5.

With the compound semiconductor shown in Fig. 1A, a polarization-induced sheet charge density σ1 of a negative value such as 10 1 3 electrons/cm 2 is usually formed at the interface between the active region 5 and the lower plating layer 4. A positive magnitude of sheet charge density σ2 is formed at the interface between the active region 5 and the upper plating layer 6. The polarity of these charges depends on the bonding of the crystal layers. In general, the sheet charge density will depend on the spontaneous factors resulting from the difference in composition between the two layers and the piezoelectric stress resulting from the lattice mismatch between the layers. For example, σ1 between the In 0 . 2 Ga 0 . 8 N active region 5 and the GaN plating layer 4 is about 8.3×10 1 2 electrons/cm 2 . This is attributed to the 20% indium content (spontaneous polarization) in the active region of In 0 . 2 Ga 0 . 8 N, and the stress in the layer due to lattice mismatch with the underlying GaN layer (piezoelectric polarization) .

Figure 1B illustrates an energy band corresponding to the structure of the device of Figure 1A. The naturally occurring polarization field produced by σ1 and σ2 reduces efficiency in many ways while the device is in operation. First, the dipole causes spatial separation of electrons and holes in the region (movement in the opposite direction). As illustrated, the hole in the valence band E v is attracted to the negative charge σ1 at one end of the active region 5, and the electrons in the conductive band E c are attracted to the positive charge σ2 at the other end. This spatial separation of free carriers reduces the probability of radioactive recombination and reduces the efficiency of the emission. Second, the energy barrier of the conductive strip and the valence band quantum well is reduced by the quantization effect associated with the electric field. Thus, E v E c of the above and the following carrier path indicated by the broken line A and the well to escape. Third, the presence of a polarization-induced field also causes the carrier to overshoot from the higher E c level on the σ1 side of the active region to the lower E v level on the σ 2 side and lower from the σ 2 side of the active region. The E v level is suddenly increased to the higher E c level on the σ1 side, as illustrated by the carrier track B.

In accordance with an embodiment of the present invention, a semiconductor light emitting device includes a light emitting layer sandwiched between two spacer layers. The difference between the net polarization in at least one of the spacer layers and the net polarization in the luminescent layer is less than the net polarization in a device having a conventional spacer layer such as a GaN spacer layer. The difference between the net polarization in at least one of the spacer layers and the net polarization in the luminescent layer is less than about 0.02 C/m 2 . In some embodiments, at least one of the spacer layers is a quaternary alloy of aluminum, indium, gallium, and nitrogen.

Matching the spacer layer to the net polarization in the luminescent layer shifts the polarization induced sheet charge from the interface between the spacer layer and the luminescent layer to the interface between the p-type region and the n-type region and the spacer layer. Once the sheet charge is separated from the luminescent layer, in some embodiments, the interface between the p-type region and the n-type region and the spacer layer is doped, which reduces the polarization field across the luminescent layer. Thus, matching the spacer layer to the net polarization in the luminescent layer and counteracting the sheet charge by doping avoids the inefficiencies caused by the polarization described above.

Figure 2 illustrates an apparatus in accordance with several embodiments of the present invention. An n-type region 21 is formed on a suitable substrate 20, typically sapphire, SiC or GaN. The active region 23 is sandwiched between two separator layers: between the n-type separator layer 22 and the p-type separator layer 24. The active region 23 can be a single luminescent layer or can comprise one or more quantum well layers separated by a barrier layer. A p-type region 25 is formed on the p-type spacer layer 24. The p-contact 26 provides electrical contact to the p-side of the active region, and the n-contact 27 provides electrical contact to the n-side of the active region. Two possible configurations of the p-contact and the n-contact are described below in Figures 7-10.

In some embodiments of the invention, one or more of the p-type spacer layer 24, the n-type spacer layer 22, and the barrier layer separating the quantum wells in the multi-quantum well active region may be aluminum, indium, gallium, and nitrogen. The quaternary alloy. The components of aluminum, indium and gallium in the barrier layer and/or the spacer layers 22 and 24 are selected to match the net polarization in the light-emitting layer of the active region 23, or the light-emitting layer and the spacer layer and/or barrier of the active region The net polarization difference between the layers is minimized. The net polarization in each layer is the sum of spontaneous and piezoelectric polarization. The desired quaternary component in the barrier layer and/or the barrier layer is based on the composition of the active region, which together with the structure of the active region determines the color of the light emitted by the active region. The quaternary layer can be grown by techniques known in the art such as gas pressure growth or pulsed organometallic chemical vapor deposition (also known as pulse atomic layer epitaxy). For a description of pulsed organometallic chemical vapor deposition, see, for example, J. Zhang et al., "Pulsed Atomic Layer Epitaxy of Quaternary Al InGaN Layers" (79 Appl. Phys. Lett. 925 (2001)) and C. Chen et al. "Pulsed Metalorganic Chemical Vapor Deposition of Quaternary Al InGaN Layers and Multiple Quantum Wells for Ultraviolet Light Emission" (41 Jpn. J. Appl. Phys. 1924 (2002)), which is incorporated herein by reference.

The embodiments described below describe features of the quaternary separation layer. The same features can be applied to form a suitable quaternary barrier layer within the active region of the multi-quantum well.

In a first embodiment, the components of the spacer layer are selected such that the net polarization difference between the luminescent layer of the active region and the at least one spacer layer is zero. The use of a spacer layer having the same net polarization as the net polarization of the luminescent layer of the active region effectively counteracts the sheet charge at the interface between the spacer layer and the active region (shown in Figure IB). Figure 3 illustrates a portion of an energy band diagram of a device having a lightly doped or unintentionally doped active region and a spacer layer, wherein the quaternary spacer layer has the same net polarization as the net polarization of the active region (P 1 = P 2 ). Figure 3 illustrates the offset of the sheet charge at the interface between the active region and the spacer layer on either side (e 1 = e 2 ). Figure 3 also illustrates that the resulting curve in the sheet charge and energy band diagram is not completely eliminated, but the interface between the self-active region and the spacer layer is displaced to the interface between the spacer layer and the p-type region and the n-type region.

In a second embodiment, the components of the spacer layer are selected such that the barrier height is sufficient to provide sufficient barrier, but the difference in net polarization between the luminescent layer and the spacer layer of the active region is less than a conventional separation such as a GaN spacer layer The net polarization in the device of the layer. The barrier height is defined as the difference between the energy band gap in the spacer layer and the energy band gap in the active layer. Generally, the higher the composition of aluminum and gallium in the quaternary triad nitride layer, the more difficult it is to grow a high crystal quality layer. As explained below, in most of the devices, the separator layer according to the first embodiment has a high composition of aluminum and indium. Although the device of the second embodiment does not completely offset the sheet charge at the interface between the separation layer and the active region, such devices have a potentially smaller sheet charge than devices having conventional barriers, and are more implementation than the first implementation. For example, the device has a partition layer with potentially better crystal quality. Both effects can increase the efficiency of the device according to the second embodiment.

Figure 4 illustrates how the appropriate components for the separator layers of the first and second embodiments are determined for a given active area component. 4 is a profile plot of polarization and energy bandgap of an Al x In y Ga z N film to an aluminum nitride component and an indium nitride component. It is assumed that an Al x In y Ga z N film is continuously grown on GaN. The solid outline represents net polarization with C/m 2 . The virtual outline represents the energy band gap by eV. DESCRIPTION OF FIG. 4 example 10% indium InGaN active layer of In 0. 1 Ga 0. 9 N ( labeled "active"), which when biased to emit blue light may be cis. In 0 . 1 Ga 0 . 9 N has an energy band gap of about 3.1 eV and a net polarization of about 0.01 C/m 2 . In the example given in Figure 4, the minimum barrier height is arbitrarily selected to be 0.2 eV. In other embodiments, the minimum barrier height may be larger or smaller, such as 0.3 eV or 0.1 eV.

Following 0.01 C in the direction of increasing the indium composition and increasing the aluminum component until reaching a component having an energy band gap of at least 3.3 (approximately Al 0 . 2 0 In 0 . 2 2 Ga 0 . 5 8 N) The /m 2 contour determines the range of components used for the spacer layer according to the first embodiment, wherein the spacer layers have the same net polarization as the net polarization of the active region. Any separation layer component at or above this point along the 0.01 C/m 2 contour line (the solid line labeled "first" on Figure 4) will provide a barrier height of at least 0.2 eV and have a net with the active area The same polarization is polarized.

The range of components used for the spacer layer of the second embodiment is illustrated as the shaded area "A" in Figure 4, wherein the spacer layers have a minimum barrier height and a net polarization less than the net polarization of the conventional spacer layer. . After representing the outline of the minimum barrier height of 0.2 eV, a curve between In 0 . 0 3 Ga 0 . 9 7 N and about Al 0 . 2 0 In- 0 . 2 2 Ga 0 . 5 8 N is taken as This area is at the boundary on the bottom right hand side. a curve between about Al 0 . 2 0 In 0 . 2 2 Ga 0 . 5 8 N and about Al 0 . 4 5 In 0 . 3 4 Ga 0 . 2 1 N (which represents the composition range of the first embodiment) ) as the boundary of area A on the top right hand side. After representing the net polarization of the GaN spacer layer (labeled "GaN" in Figure 4), a curve between about GaN and about Al 0 . 4 5 In 0 . 2 6 Ga 0 . 2 9 N As the boundary of the area A on the left hand side. Any spacer component within this shaded region will have a barrier of at least 0.2 eV and a net polarization less than the net polarization of the GaN spacer. The solid line in region A represents a spacer layer component having a barrier height that is the same as the barrier height of the GaN spacer layer, but less than the net polarization of the GaN spacer layer.

FIG 5 illustrates an example of a 20% indium InGaN active layer of In 0. 2 Ga 0. 8 N, which may be biased to emit green light when in cis. The In 2 . 2 Ga 0 . 8 N active region (labeled "active") has a net polarization of about 0.021 C/m 2 and an energy band gap of about 2.9 eV. In the example given in Figure 5, the minimum barrier height is again arbitrarily selected to be 0.2 eV.

By following the 0.021 C/m 2 contour to a component with an energy band gap difference of at least 0.2 eV (approximately Al 0 . 1 7 In 0 . 2 8 Ga 0 . 5 5 N, which has 3.1 eV) Energy Band Gap) The range of components for the separator layer according to the first embodiment can be determined, wherein the separator layers have the same net polarization as the net polarization of the active region. Any component at or above this point along the 0.021 C/m 2 contour (the solid line labeled "first" in Figure 5) will provide a sufficiently high barrier spacer and have a net polarization with the active region The same net polarization.

The range of components used for the spacer layer according to the second embodiment is illustrated as the shaded region "B" of FIG. 5, wherein the spacer layers have a minimum barrier height and a net width less than the net polarization of the conventional GaN spacer layer. Chemical. After the representative minimum barrier height of 0.2 eV contour line, approximately In 0. 1 2 Ga 0. 8 8 N and about Al 0. As one of this curve between 1 7 In 0. 2 8 Ga 0. 5 5 N The area is at the boundary on the right hand side of the bottom. A curve between about Al 0 . 1 7 In 0 . 2 8 Ga 0 . 5 5 N and about Al 0 . 4 5 In 0 . 4 0 Ga 0 . 1 5 N (which represents the composition range of the first embodiment) ) as the boundary of area B on the top right hand side. After representing the contour of the net polarization of the GaN spacer layer (labeled "GaN"), a curve between about GaN and about Al 0 . 4 5 In 0 . 2 6 Ga 0 . 2 9 N is taken as region B. The boundary on the left hand side. Any spacer component within this shaded region will have a barrier of at least 0.2 eV and a net polarization less than the net polarization of the GaN spacer. The solid line in region B represents a spacer layer component having a barrier height that is the same as the barrier height of the GaN spacer layer, but less than the net polarization of the GaN spacer layer.

Although Figures 4 and 5 terminate in 45% of the aluminum nitride and indium nitride components, layers having higher aluminum nitride and indium nitride compositions may be suitable. The data shown in Figures 4 and 5 is not intended to limit the invention. The data in Figures 4 and 5 were calculated using techniques well known in the art and using the following material parameters. If different values are used for the following material parameters, the data shown in Figures 4 and 5 can be changed.

The data in Figures 4 and 5 were calculated as follows. Given the a-lattice constant a k and the elastic constant c i j , k of AlN, GaN and InN, the a-lattice constant a A l I n G of a quaternary layer grown on GaN can be calculated according to the following equation a N and stress ε z z : a AlInGaN = x . a AlN + y . a InN + z . a GaN

c ij = x . c ijAlN + y . c ijInN + z . c ijGaN gives the energy band gap E i of AlN, GaN and InN and the bending parameter b i j of each ternary alloy, and the energy band gap of the free standing quaternary layer can be calculated according to the following equation:

T ij ( x )= x . E j +(1- x ). E i + b ij . x (1- x ) u =(1- x + y )/2 v =(1- y + z )/2 w =(1- x + z )/2 The energy of the strained quaternary layer grown on GaN The bandgap (shown in phantom lines in Figures 4 and 5) is related to the stress ε Z Z of the layer (calculated above) and the energy band gap of the free-standing material, which is based on the following equation: E ε = 15.4 . ε zz E g = E AlInGaN + E ε Given the spontaneous polarization P s p , k of the AlN, GaN and InN and the piezoelectric constant e i j , k , the quaternary growth on GaN can be calculated according to the following equation The spontaneous polarization of the layer p s p and the piezoelectric polarization P p z : P sp = x . P spAlN + y . P spInN + z . P spGaN P pz =2. e 3 1 . ε xx + e 3 3 . ε zz e ij = x . e ijAlN + y . e ijInN + z . e ijGaN then gives the net polarization of the quaternary layer grown on GaN by the following equation: P =( P sp - P spGaN ) + P pz as shown in Figure 3, matching the separation layer with the net polarization of the active region The sheet charge at the interface between the separation layer and the active region. These sheet charges are displaced to the interface between the p-type region and the n-type region and the spacer layer, wherein the difference in composition between the layers forming the interface results in a different net polarization on either side of the interface. Removing the sheet charge from the active region does not completely eliminate its effect on the active region. The "tilt" of the energy band in the active region shown in Figure 3 is caused by the sheet charge at the interface between the spacer layer and the p-type region and the n-type region.

In order to eliminate the sheet charge, U.S. Patent No. 6,515,313 teaches "incorporating various dopants into a semiconductor. The dopant impurities should be of a type that does not diffuse from their intended position. The dopants are ionized to positive based on their energy levels. Or a negatively charged state that is opposite to the state of charge induced by interfacial polarization to counteract or reduce its effect. "U.S. Patent 6,515,313 incorporates a dopant at the interface between the separation layer and the active region. Incorporating dopants (especially Mg) so close to the active region can degrade the crystal quality of the active region.

In some embodiments of the invention, the spacer layer is sufficiently thick to "occlude" the active region from the p-type region and the sheet charge at the interface between the n-type region and the spacer layer, followed by a neutralizing sheet The dopant of the charge is doped with an interface with a sheet charge to eliminate the sheet charge. In embodiments that do not have a thick spacer layer, the spacer layer typically has a thickness of between about 50 angstroms and about 200 angstroms. In embodiments having a thick spacer layer, the spacer layer can have a thickness between about 500 angstroms and a critical thickness of the spacer layer (defined as the maximum spacer thickness that can be grown without cracking or relaxing). The thick spacer layer typically has a thickness of between about 200 angstroms and about 1000 angstroms. In general, the thickness of the thick spacer layer is chosen to be thick enough to shield the active region from the dopant to counteract the sheet charge and is chosen to be thin enough to allow for the growth of a high crystal quality spacer layer.

The negative charge is concentrated at the interface between the n-type or undoped spacer layer 22 and the n-type region 21. This sheet charge can be counteracted by incorporating a highly n-doped material region as close as possible to the interface. The highly doped regions may be in portions of the n-type region 21 or the spacer layer 22 adjacent to the interface. For example, the thickness may be 10 angstroms and has about 1 × 10 1 8 cm - 3 and 2 0 cm 1 × 10 - 3 region of the Si concentration of the n-type region 21 is incorporated in the spacer layer 22 or, directly adjacent to the The interface between these two layers. More preferably, the highly doped region of about 5 × 10 1 9 cm - 3 and 1 × 10 2 0 cm - Si concentration of between 3. Similarly, positive film charges are concentrated at the interface between the p-type spacer layer 24 and the p-type region 25. This sheet charge can be counteracted by incorporating a highly p-doped material region into a portion of p-type region 25 or spacer layer 24 adjacent to the interface. For example, the thickness may be 10 angstroms and has about 1 × 10 1 8 cm - 3 and 2 0 cm 1 × 10 - 3 regions of the Mg concentration of the p-type region 25 is incorporated in the spacer layer 24 or directly adjacent to the The interface between these two layers. More preferably, the highly doped region of about 5 × 10 1 9 cm - 3 and 1 × 10 2 0 cm - Mg concentration of between 3.

The amount of doping required at the interface between the spacer layer and the p-type region and the n-type region may depend on the magnitude of the sheet charge, which is dependent on the composition of the layers in the device. Typically, the thickness and dopant concentration are selected such that the dopant concentration in the highly doped region multiplied by the height of the highly doped region is approximately equal to the sheet charge at the interface. Therefore, the higher the dopant concentration in the highly doped region, the thinner the thickness required to counteract the sheet charge. In some embodiments, the sheet charge can be counteracted by incorporating a lower concentration of dopant into the n-type region and the p-type region or the spacer layer over a greater thickness. In addition, as the composition of indium in the active region increases, the magnitude of the sheet charge increases. In the examples given above, the sheet charge in a device with a 20% indium quantum well may be twice the amount of sheet charge in a device with a 10% indium quantum well.

Figure 6 is an energy band diagram of a device in which the spacer layer has the same net polarization as the active region and is doped with a thick spacer layer and at the sheet charge interface to eliminate the sheet charge. As shown in Fig. 6, the bending of the energy band at the interface between the layers and the tilt of the energy band in the active region are eliminated.

Figure 7 is a plan view of a small junction device (i.e., an area of less than one square millimeter). Figure 8 is a cross section taken along line CC of the device shown in Figure 7. Figures 7 and 8 illustrate the configuration of contacts that can be used with any of the epitaxial structures 30 shown in Figure 2 and described above. The device shown in Figures 7 and 8 has a single via 31 that is etched down to the n-type layer below the active region of the epitaxial structure 30. The n-contact 27 is deposited in the via 31. The n-channel 31 is located in the center of the device to provide uniformity of current and light emission. The p-contact 26 provides electrical contact to the p-side of the active region of the epitaxial structure 30. One or more dielectric layers 32 separate the n-contact 27 from the p-contact 26. A p submount connection 34 (eg, a wettable metal for soldering to the solder) is connected to the p-contact 26, and an n-sub-substrate connection 33 is connected to the n-contact 27.

As shown in FIG. 7, the device is connected to a sub-substrate by three sub-substrate connections: two p-sub-substrate connections 34 and one n-sub-substrate connection 33. The n-substrate connection 33 can be located anywhere within the n-contact region 27 (surrounded by the insulating layer 32) and need not be located directly on the via 31. Similarly, the p-sub-substrate connection 34 can be located anywhere on the p-contact 26. As a result, the connection of the device to the sub-substrate is not limited by the shape or placement of the p-contact 26 and the n-contact 27.

Figure 9 is a plan view of a large junction device (i.e., an area greater than or equal to 1 square millimeter). Figure 10 is a cross section taken along the axis DD of the device of Figure 9. 9 and 10 also illustrate the configuration of contacts that can be used with any of the epitaxial structures 30 shown in FIG. 2 and described above. The active region of the epitaxial structure 30 is divided into four regions separated by three trenches in which the n-contact 27 is formed. Each region is connected to a sub-substrate by four p-sub-substrate connections 34 formed on p-contact 26. The n junction 27 surrounds the four active regions. The n-contact 27 is connected to a sub-substrate by six n-sub-substrate connections 33. The n-contact and the p-contact can be electrically isolated by the insulating layer 32.

Figure 11 is an exploded view of a packaged light emitting device. A heat-sinking slug 100 is placed in an insert-molded lead frame. The insert molded lead frame is, for example, a filled plastic material 105 formed around a metal frame 106 that provides an electrical path. Block 100 can include an optional reflective cup 102. The light emitting device die 104, which may be any of the devices described above, is mounted to the block 100 directly or indirectly via the thermally conductive submount 103. An optical lens 108 can be added.

Reducing the effect of the polarization field on the active region in accordance with embodiments of the present invention can have several advantages. First, the carrier recombination rate can be increased, increasing the quantum efficiency of the device. Second, the carrier lifetime can be reduced, reducing the carrier density at a given current density, and resulting in improved quantum efficiency at increased drive current. Third, electron and hole injection efficiency may increase, resulting in a more uniform filling of the active region by the carrier. Each of these effects can improve the efficiency of the device.

Having described the present invention in detail, it will be apparent to those skilled in the art that the present invention may be modified, without departing from the spirit of the inventive concept described herein. Therefore, the scope of the invention is not intended to be limited to the particular embodiments illustrated and described.

1. . . Substrate layer

2. . . The buffer layer

3. . . N-type contact layer

4. . . Plating

5. . . Active area

6. . . Plating

7. . . P-type GaN conductive contact layer

20. . . Substrate

twenty one. . . N-type region

twenty two. . . N-type spacer

twenty three. . . Active area

twenty four. . . P-type spacer

25. . . P-type region

26. . . p contact

27. . . n contact

30. . . Epitaxial structure

31. . . path

32. . . Insulation/dielectric layer

33. . . n sub-substrate connection

34. . . P sub-substrate connection

100. . . Heat sink

102. . . Reflective cup

103. . . Thermal conduction submount

104. . . Illuminating device die

105. . . Filled plastic material

106. . . metal frame

108. . . optical lens

1A and 1B are cross-sectional and energy band diagrams of a portion of a prior art illumination device described in U.S. Patent No. 6,515,313.

2 is a cross-sectional view of a device in accordance with an embodiment of the present invention.

Figure 3 is an energy band diagram of a device having the same net polarization as the separation layer and the active region.

Figures 4 and 5 are graphs of the aluminum component versus indium component for a quaternary triad nitride layer, including contours showing bandgap energy and net polarization.

Figure 6 is an energy band diagram of a device in which the spacer layer has the same net polarization as the active region and is doped with a thick spacer layer and at the sheet charge interface to eliminate the sheet charge.

7 and 8 are plan and cross-sectional views of a small junction light-emitting device.

9 and 10 are plan and cross-sectional views of a large junction light-emitting device.

Figure 11 is an exploded view of a packaged light emitting device.

20. . . Substrate

twenty one. . . N-type region

twenty two. . . N-type spacer

twenty three. . . Active area

twenty four. . . P-type spacer

25. . . P-type region

26. . . p contact

27. . . n contact

30. . . Epitaxial structure

Claims (41)

  1. A semiconductor light emitting device comprising: first and second spacer layers; and a light emitting layer sandwiched between the first and second spacer layers; wherein a net polarization of at least one of the spacer layers a difference between a net polarization in the luminescent layer is less than a difference between a net polarization in GaN and the net polarization in the luminescent layer, and at least one of the spacer layers A difference between the net polarization and the net polarization in the luminescent layer is less than 0.02 C/m 2 .
  2. The device of claim 1, wherein at least one of the spacer layers comprises Al x In y Ga z N, wherein 0<x 1,0<y 1 and 0<z 1.
  3. The device of claim 1, wherein the luminescent layer comprises at least one InGaN layer.
  4. The device of claim 1, wherein the difference between the net polarization in at least one of the spacer layers and the net polarization in the light-emitting layer is less than 0.01 C/m 2 .
  5. The device of claim 1, wherein the difference between the net polarization in at least one of the spacer layers and the net polarization in the light-emitting layer is less than 0.005 C/m 2 .
  6. The device of claim 1, wherein the difference between the net polarization in the at least one spacer layer of the spacer layer and the net polarization in the light-emitting layer is about 0 C/m 2 .
  7. The device of claim 1, wherein a difference between an energy band gap in at least one of the spacer layers and an energy band gap in the light-emitting layer is greater than 0.1 eV.
  8. The device of claim 1, wherein a difference between an energy band gap in at least one of the spacer layers and an energy band gap in the light-emitting layer is greater than 0.2 eV.
  9. The device of claim 1, wherein the luminescent layer comprises at least one InGaN layer having a composition between In 0 . 0 5 Ga 0 . 9 5 N and In 0 . 1 5 Ga 0 . 8 5 N.
  10. The device of claim 9, wherein: at least one of the spacer layers is a quaternary alloy of aluminum, indium, gallium, and nitrogen; and one of the aluminum alloy partition layers has a aluminum component greater than or equal to 20% .
  11. The device of claim 10, wherein the indium component of the quaternary alloy separator layer is greater than or equal to 22%.
  12. The device of claim 9, wherein at least one of the spacer layers is a quaternary alloy of aluminum, indium, gallium, and nitrogen.
  13. The device of claim 9, wherein at least one of the separator layers is a quaternary alloy of aluminum, indium, gallium, and nitrogen; and one of the aluminum component of the quaternary alloy separator is greater than zero and less than or equal to 20%; and one of the indium components in the quaternary alloy separator layer is greater than zero and less than or equal to 22%.
  14. The apparatus of 1, wherein the at least one light emitting layer comprises an InGaN layer having In 0. 1 5 Ga 0. 8 5 N and 0. 5 Ga One component between 0. 5 N In the request entries.
  15. The device of claim 14, wherein: at least one of the spacer layers is a quaternary alloy of aluminum, indium, gallium, and nitrogen; and one of the aluminum alloy partition layers has an aluminum component greater than or equal to 17% .
  16. The device of claim 15 wherein the indium component of the quaternary alloy separator layer is greater than or equal to 28%.
  17. The device of claim 14, wherein the at least one spacer layer of the spacer layer is a quaternary alloy of aluminum, indium, gallium, and nitrogen.
  18. The device of claim 14, wherein at least one of the spacer layers is a quaternary alloy of aluminum, indium, gallium, and nitrogen; and one of the aluminum component of the quaternary alloy separator is greater than zero and less than or equal to 17%; and one of the indium components in the quaternary alloy separator layer is greater than zero and less than or equal to 28%.
  19. The device of claim 1 wherein at least one of the separator layers has a thickness between about 200 angstroms and about 1000 angstroms.
  20. The device of claim 1 wherein the at least one spacer layer of the spacer layer has a thickness between about 200 angstroms and a critical thickness of the one of the spacer layers.
  21. The device of claim 1, further comprising: an n-type region adjacent to a surface of the first spacer layer opposite to the light-emitting layer; and an adjacent one of the light-emitting layers adjacent to the second spacer layer The p-type area of the surface.
  22. The device of claim 21, further comprising a highly doped n-type material region adjacent to an interface between the first spacer layer and the n-type region, the highly doped n-type material region having about 1 × 10 1 8 cm - 3 and about 1 × 10 2 0 cm - one 3 and a dopant concentration between about 10 angstroms and about 100 angstroms thickness between one.
  23. The apparatus of Item 22 of the request, wherein the highly doped n-type material of the region of about 5 × 10 1 9 cm - 3 and about 1 × 10 2 0 cm - one dopant concentration between 3.
  24. The device of claim 22, wherein the highly doped n-type material region is located within the first spacer layer.
  25. The device of claim 22, wherein the highly doped n-type material region is located within the n-type region.
  26. The device of claim 21, further comprising a highly doped p-type material region adjacent to an interface between the second spacer layer and the p-type region, the highly doped p-type material region having about 1 × 10 1 8 cm - 3 and about 1 × 10 2 0 cm - one 3 and a dopant concentration between about 10 angstroms and about 100 angstroms thickness between one.
  27. The apparatus of the requested item 26, wherein the highly doped p-type material of the region of about 5 × 10 1 9 cm - 3 and about 1 × 10 2 0 cm - one dopant concentration between 3.
  28. The device of claim 26, wherein the highly doped p-type material region is located within the second spacer layer.
  29. The device of claim 26, wherein the highly doped p-type material region is located within the p-type region.
  30. The device of claim 1, wherein the luminescent layer is a first quantum well, the device further comprising a second quantum well and a barrier layer disposed between the first quantum well and the second quantum well.
  31. The device of claim 30, wherein the barrier layer comprises Al x In y Ga z N, wherein 0<x 1,0<y 1 and 0<z 1.
  32. The device of claim 30, wherein a net polarization in the barrier layer is less than a net polarization in the GaN, and the net polarization in the barrier layer is at least one of the quantum wells A difference between polarizations is less than 0.02 C/m 2 .
  33. The device of claim 30, wherein the difference between the net polarization in the barrier layer and the net polarization in at least one quantum well of the quantum wells is less than 0.01 C/m 2 .
  34. The device of claim 30, wherein the difference between the net polarization in the barrier layer and the net polarization in at least one quantum well of the quantum wells is less than 0.005 C/m 2 .
  35. The device of claim 30, wherein the difference between the net polarization in the barrier layer and the net polarization in at least one quantum well of the quantum wells is about 0 C/m 2 .
  36. The device of claim 1, wherein the luminescent layer comprises Al x In y Ga z N, wherein 0<x 1,0<y 1 and 0<z 1.
  37. A semiconductor light emitting device comprising: first and second spacer layers; and an active region sandwiched between the first and second spacer layers, the active region comprising a first quantum well, a second quantum well and a a barrier layer disposed between the first quantum well and the second quantum well; wherein a difference between a net polarization in the barrier layer and a net polarization in at least one quantum well of the quantum wells a difference between a net polarization in GaN and the net polarization in at least one quantum well of the quantum wells, and the net polarization in the barrier layer is in at least one quantum well of the quantum wells A difference between the net polarizations is less than 0.02 C/m 2 .
  38. The device of claim 37, wherein the barrier layer comprises Al x In y Ga z N, wherein 0<x 1,0<y 1 and 0<z 1.
  39. The device of claim 37, wherein the difference between the net polarization in the barrier layer and the net polarization in at least one quantum well of the quantum wells is less than 0.01 C/m 2 .
  40. The device of claim 37, wherein the difference between the net polarization in the barrier layer and the net polarization in at least one quantum well of the quantum wells is less than 0.005 C/m 2 .
  41. The device of claim 37, wherein the difference between the net polarization in the barrier layer and the net polarization in at least one quantum well of the quantum wells is about 0 C/m 2 .
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